Coating material



April 28, 1942. w. c. TOLAND ET AL 2,280,985

CQATING MATERIALS Filed Jan. 16, 1941 Izwezzfonr i flifoa neg PatentedApr. 28, 1942 FFICE 2,280,988 COATING MATERIAL William Craig line, Mass,trustee Toland and Ellis Bassist, Brookalsig'nors to William CraigToland,

Application January 16, 1941, Serial No. 374,694

14 Claims.

This invention relates to printing and more especially to novelcombinations of materials for use in printing plates.

A principal object of the invention is to improve planographic printingand to devise a planographic printing plate with non-printing portionsmade up of novel combinations of materials which impart improvedprinting ability, durability, and other desirable characteristics to theplate. Another object of the invention is to provide improvements inmethods of making planographic printing plates, and in particular toimprove methods of bonding grease-receptive colloid printing portions towater-receptive coatings on a lithographic support. The invention alsoaims to provide a simple, cheap and efllcient planographic plate ofnovel controlled waterreceptivity.

- The nature of the invention and its objects will be more fullyunderstood from the following description of the drawing and discussionrelating thereto.

In the accompanying drawing:

Fig. 1 is a fragmentary elevational view of the printing plate of theinvention;-and

Fig. 2 is a fragmentary elevational view of a modified printing platestructure.

Figs. 1 and 2 of the drawing illustrate planographic printing plates ofthe type in which a hydrophilic material is utilized to constitute theink-repellent non-printing portions. Plates of this character aresometimes referred to in the printing art as "colloid" printing platesand it is intended that the word plates as hereinafter employed in thespecification shall refer to colloid printing plates. The wordhydrophilic as employed in the specification means waterabsorptive andwater-retentive but water-insoluble.

In an earlier Patent No. 2,230,981, issued February 4, 1941, We havedisclosed and claimed synthetic resins adapted to function as ahydrophilic material of the character described. An example of thesynthetic resins is a hydrophilic vinyl compound, as polyvinyl alcohol.The vinyl resin, for example in the form of a powder, is dissolved inhot water and may be readily coated on a lithographic support, forming afilm which will absorb cold water but is not dissolved by it. Theprinting portions for a plate of this type may be prepared by theconventional albumin process, in which a coating of bichromated albuminis applied over the vinyl resin coating described. The bichromatedalbumin is allowed to dry, exposed to .actinlc light passed through acontact scribed. The

negative. covered with greasy developing ink, and washed in the usualmanner in water.

We have discovered that coatings for forming the non-printing portionsof plates, particu larly coatings of vinyl compounds, are improved byhaving small amounts of water-repellent materials dispersed therein. Inattempting to introduce water-repellent substances intb a coating of awater-receptive material, considerable difliculty is encountered sincethe two types of materials repel one another and refuse to becomeintimately mixed together.

In accordance with a preferred embodiment of the invention, weincorporate suspensions of water-repellent substances with an aqueoussuspension of hydrophilic material to provide a novel coating. mixture.In mixing the two liquids, we make use of an emulsifying agent such as aclay, or other finely divided inert substance, to secure intimateincorporation of the ingredients with one another, and to provide acoating mixture of uniform consistency adapted to being applied in athin uniform film.

Referring in. detail to the drawing, Fig. l illustrates a preferredembodiment of the plate of the invention, in which numeral i denotes alithographic support or base, preferably composed of paper andwater-repellent materials laminated together to provide a substantiallywaterproof sheet. If desired, other base substances may be employed, asmetals, plastics, and the like. Overlying the base I is a coating 2formed from a coating mixture of water-receptive and water-repellentmaterials, as decoating 2 forms the non-printing portions of the plate,presenting grease-repellent surfaces In. Numeral 3 indicates printingportions prepared for example by the albumin process above noted.

For example, one suitable coating mixture may include a 5% solution ofpolyvinyl alcohol, with which is combined a filler of a finely dividedmaterial such as calcium carbonate, china clay, and the like, and awater-repellent substance such as the solid product obtained from a 10%dispersion in water of urea formaldehyde glue, as for example Cascoresin glue, in an amount sufficient to constitute 2% to 3% of the polyvinyl alcohol present Other desirable substances. which may be employedare gelatin, sodium silicate, and various water-repellent resins.

The filler acts as an emulsifying agent, which allows water-repellentsubstances to be uniformly dispersed throughout and held in suspensionsin the alcohol suspension.

of water-receptive compounds. This providesa coating mixture which canbe readily applied on a surface such as paper, and which adheres to thesurface without cracking or forming lumps.

Th filler also tends to reduce swelling of the hydrophilic material, andto provide a hard mass having a grain resembling that of lithographic aprinting portions to break away from the coating when exposed toextended press operation. The water-repellent substance in the plate ofthe invention provides a body for which photographically hardenedalbumin has a definite aflinity, and thereby serves as a supportingmedium around which the albumin can become more firmly anchored. Sincethe water-repellent substance is dispersed throughout the hydrophiliccoating and since the albumin, which forms the printing portions, isadapted to sink in and become impregnated throughout the coating, thereis obtained a greatly improved bonded relation between the albumin andthe coating generally. As a result, more durable printing portions areeffected.

Another feature of the invention is the improved water-receptivecharacter of the hydrophilic coating 2 when combined with small amountsof a water-repellent substance. Substances such as the urea formaldehyderesin, and others noted, exert a slight water-repellent action withinthe body of the coating and thereby provide a means of reducing orcontrolling the water-receptivity of the coating without impairing itsefiectiveness. Also, the presence of water-repellent substance dispersedthroughout a hydrophilic coating tends to reduce and control swelling ofthe coating. This is important for the reason that too much swellingintroduces a variable factor into the ink-repelling ability ofnon-printing portions of a plate, and is highly objectionable. Acarefully limited amount of swelling, however, may be veryadvantageously utilized to accentuate or more sharply define thenon-printing portions in the surface of a plate, and thereby securesharper printing.

In Fig. 2, we have illustrated a plate made up of a base i, having ahydrophilic coating 2b,

ing portions 3. The coating 2b includes a stratum of water-repellentmaterial lightly impregnated part way therethrough. The water-repellentmaterial combined with the water-receptive material constitutesarelatively small proportionate part of the coating 2b and therebyallows the coating to continue to function as a water-receptive body. Aplate having such a stratum of water-repellent material is preferablyformed by adding the water-repellent material after a hydrophiliccoating is applied on a lithographic base and after printing portionshave been formed on the coating. A dispersion or suspension of amaterial as sodium silicate may, for example, be brushed or flowed overthe printsink into the hydrophilic coating. Other modes of applicationmay be resorted to, as for example by dipping the plate in a bath ofwater-repellent material.

The stratum 4 is desirable as a means for modifying thewater-receptivity of the hydrophilic coating 2 since it provides ahydrophilic coating, a part of which may absorb very little water.Application of water-repellent material over a finished plate surfacemay also benefit the printing portions, tending to harden them, to morefirmly anchor them on the hydrophilic coating, and to sharpen their inkreceptivity.

taking advantage of the ability of the gelatin to contract upon itself.The grained surface thus obtained is effective in carrying outcontinuous tone printing.

The use of gelatin is also illustrative of the step of mixing with awater-receptive coating material a substance which is soluble in waterbut which in a water-solution form may be rendered water-repellent. Forexample, a coating obtained from a mixture of a gelatin solution andavinyl solution may be treated as .by heat presenting non-printingsurfaces in, and printing and non-printing portions, and allowed to 7vinyl resin noted above.

and/or chemical reagents such as iron chloride, etc., to render thegelatin hard and water-repellent. In this way we are enabled toincorporate a fine dispersion of a water-repellent substance in ahydrophilic compound without having to resort to the use of anemulsifying agent such as clay. Certain other colloids as albumin, gumarabic, and the like, may be similarly employed.

It is pointed out that the mixture of a waterreceptive vinyl resincoating suspension with a water-repellent ureaiormaldehyde resin glue,as carried out by the use of a filler material in accordance with theinvention, provides a novel coating compound which has not heretoforebeen available and which may be utilized for other purposes thanprinting; for example, as a special type of adhesive and in otherconnections.

Another aspect of the invention, is the provision of novel combinationsof filler materials employed in conjunction with hydrophilic substancesto form coatings for planographic printing plates. It has been foundthat very desirable results are obtained from mixing different types offiller materials with hydrophilic substances. For example, a such aschina clay may be mixed with a relatively coarser filler such as silicaof a particle size found in the product :Silex. or similar bodies, andthe two fillers then thoroughly incorporated in a hydrophilic coatingsubstancesuch as the A coating, obtained from a mixture of this typepresents a greatly improved grained surface, due to the presence of therelatively coarse filler particles. At the same time undesirableporosity, such as may resuit from the use of coarse particles, isprevented by the fine filler particles. The relatively sharper grainedsurface formed from coarse filler particles is capable of retainingmoisture by capillarity in addition to absorption, to improve thewater-retentive character of the coating. If desired, the sharplydefined grain may be modified by coating with a weak solution of ahydrophilic compound such as 111% solution of polyvinyl alcohol,Preferablybne part of coarse finely divided filler.

filler should be employed with four parts of fine filler. Otherproportions may be resorted to and other materials than china clay,silica and the like utilized.

It will be seen that the invention provides a novel printing platehaving improved printing and non-printing portions. A method is providedof more solidly anchoring, on ,a hydrophilic coating, colloid materialsforming the printing portions of a plate. Improvements are also providedin connection with the water-retentive character of hydrophiliccoatings. Means are set forth for controlling swelling, imparting novelgrained surface character, and generally providing a cheap, simple andefficient printing plate. The invention also provides novel combinationsof filler materials with hydrophllic substances.

While we have shown a preferred embodiment of the invention, it shouldbe understood that modifications may be resorted to, in keeping with thespirit of the invention as defined by the appended claims.

Having described our invention, ,we claim:

1. As an article of manufacture a planographic printing plate presentingprinting portions and non-printing portions, said non-printing portionsincluding a water-absorptive material, a filler, and a water-repellentsubstance.

2. As an article of manufacture a planographic printing plate presentingprinting portions and non-printing portions, said non-printing portions,including a coating of a vinyl compound of the type which absorbs coldwater without dissolving, said vinyl compound having a waterrepellentsubstance dispersed therein.

3. As an article of manufacture a planographic printing plate presentingprinting portions and non-printing portions, said non-printing portionsincluding a coating of a vinyl compound, a iiller, and a water-repellentsubstance, said vinyl compound occurring in a polymerized state in whichit absorbs cold water without dissolving.

4. As an article of manufacture a planographic printing plate presentingprinting portions and non-printing portions, said non-printing portionsincluding a vinyl compound of the type which absorbs cold water withoutdissolving, a filler, and a urea formaldehyde resin.

5. As an article of manufacture a planographic printingplate presentingprinting portions and non-printing portions, said non-printing portionsincluding a vinyl compound of the type which absorbs cold water withoutdissolving, a filler, and gelatin.

8. As an article of manufacture a planographic printing plate presentingprinting portions and non-printing portions, said non-printing portionsincluding a hydrophilic material, a filler, and sodium silicate.

'I. As an article of manufacture a planographic printing platepresenting printing portions and non-printing portions, saidnon-printing portions including a vinyl compound of the type whichabsorbs cold water without dissolving and selatin.

8. As an article of manufacture a planographic printing plate presentingprinting portions and non-printing portions, said non-printing portionsincluding a coating of hydrophllic vinyl material having therein astratum of water-repellent substance.

9. As an article of manufacture a planographic printing plate presentingprinting portions and non-printing portions, said non-printing portionsincluding a coating of a hydrophilic polyvinyl alcohol having therein astratum of water-repellent substance, said printing portions beingbonded to the said stratum in the hydrophilic layer.

10. As an article of manufacture, a planographic printing platepresenting printing portions and non-printing portions, saidnon-printing portions including a coating of water-receptive polyvinylalcohol, a urea formaldehyde resin, and an emulsifying agent formaintaining the urea formaldehyde resin uniformly dispersed throughoutthe water-receptive coating;

11. As an article of manufacture, a planographic printing platepresenting a base, a coating of water-receptive material overlying saidbase adapted to present non-printing portions of the plate, and agrease-receptive colloid material bonded to the said coating toformprinting portions of the plate, said water-receptive coatingincluding polyvinyl alcohol, a water-repellent substance, and anemulsifying agent for maintaining the water-repellent substanceuniformly dispersed throughout the coating, said colloid printingportions extending into the water-receptive coating and bonded with thewater-repellent substance therein.

12. In a method of making planographic printing plates the steps whichinclude applying on a lithographic base a coating of water-receptivematerial adapted to form the non-printing portions of a planographicplate, forming greasereceptive printing portions on ,a water-receptivecoating, and then impregnating a water-repellent material in the platesurface.

13. That improvement in methods of making planographic printing plateswhich comprises preparing a coating mixture which includes awater-receptive material and a colloid which is normally soluble inwater, applying a coating of the said mixture on a lithographic supportmember to form the non-printing portions of the said plate, then forminggrease-receptive printing portions on the said coating, and thentreating the plate thus formed with a reagent for rendering said colloidwater-repellent.

14. That improvement in methods of making planographic printing plateswhich comprises preparing a coating mixture including a vinyl resin andan aqueous solution of gelatin, applying a coating of the said mixtureon a lithographic support member to form water-receptive non-printingportions of the said plate, then forming grease-receptive printingportions on the said coating, and then treating the plate thus formedwith areagent for rendering the gelatin water-repellent.

WILLIAM CRAIG TOLAND. ELLIS BABSIB'I.

